Method and apparatus for flash butt welding



Nov. 22, 1949 J. H. COOPER ET AL METHOD AND APPARATUS FOR: FLASH-BUTTWELDING 2 Sheets-Sheet 1 Filed Oct. 8, 1945 JOmFZOU gwuq/yvhow H. COOPERSMITH JOSEPH CLYDE E 2 Sheets-$heet 2 H, COOPER SMITH @{IOOCGQQGQQQGQQQOQQQOOOOOOOOOOQOOOOODOV O Q 1 BI 1 q mm R o .i!onoeooooaeoooeoeooeeoooeo II... onnc a I. iiqv-u'ol A r. I m m...III.."Q.U..I J:

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J. H. COOPER ET AL, METHOD AND APPARATUS FOR FLASH-BUTT WELDING 8, 1945Nov, 22, 1949 Filed Oct.

Patented Nov. 22, 1949 METHOD AND APPARATUS FOR FLASH BUTT WELDINGJoseph H. Cooper and Clyde E. Smith, Warren,

Ohio, assignors to The Taylor-Winfield Corporation,

Warren, Ohio, a corporation of Ohio Application October 8, 1945, SerialNo. 621,102 7 Claims. (01. 219-4) This invention welding and moreparticularly to improved apparatus for controlling the welding currentduring flash welding cycles. The invention seeks to provide asubstantially improved system for controlling the strength of currentapplied to the work pieces in flash welding processes whereby theflexibility and consequently the usefulness of such control in a broadvariety of operations is materially enhanced. For example, the controlprovides for the application of an exceedingly wide range of effectivevoltages to the work pieces while enabling these Voltages to be shiftedfrom one value to another during the welding cycle either underautomatic or manual control in such manner that all critical factorswhich enter into the making of quality flash-butt welds may bemaintained under strict control.

One of the most critical of the above mentioned factors is the extentand rate of heating of the contiguous edges of the work pieces and thefinal temperature obtained therein at the time of upset. Thisnecessitates a precise correlation of voltage applied to the work pieceswith the speed of travel of the movable platen of the welding machineand because of the inherent mechanical limitations in the equipment itis more advantageous to effect the required adjustments in theelectrical aspects and the present invention provides for infiniteadjustments of the voltage applied during the stated critical period.Moreover, this precision control is effected while yet providing assistin initiating the arc and the spread of the arc throughout the weldingarea.

A further and more specific object of the invention is the provision ofimproved methods of of improved apparatus for carrying out such methods.In the Welding of Wide thin material as strip, for example, difficultyis often experienced in squaring the material in the welding machine orthe contiguous edges of the strip protruding from the dies of thewelding machine are so irregular that successful Welds are impossible ofattainment. Heretofore this condition has been met by employing in thewelding machine a squaring device either of the mechanical slitting typeor of the flame or torch machining type so that the edges of the stripare prepared for welding after the strip lengths are securely clamped inthe dies of the machine. According to the present invention the need forI, ancillary devices is avoided, the protruding and without loss ofexcessive quantities of metal. This mode of operation is made entirelypracticalby the voltage controlof the invention. I

Other objects of the invention include the provision of a practical andimproved flash-butt welder voltage control surge of current (at lowpower factor) resulting from the short-circuiting preheat and upsetcontact but is more advantageously accomplished by reducing the portionsof the successive half cycles of the current source transmitted to thetransformer. The second object is accomplished primarily by improvedpower contactor arrange ments and by employing at least one electronicpower contactor together with improved means to vary the conduction inthe same.

Another object of this invention is the provision of an improved generalcontrol system for a flash-butt welding machine wherein the integrationof voltage control systems of the nature outlined above with themechanical elements of the machine is made possible in an efiective andadvantageous manner.

The above and other objects and advantagesof the invention will becomeapparent upon consideration oi theiollowing detailed specification. andthe accompanying drawing wherein there is disclosed. a preferredembodiment of the invention.

In the drawing:

Figure 1 is a schematic representation of an electrical resistanceflash-butt welding machine constructed according to the principles ofthe invention; and

Figure 2 is a set of curves showing various voltage relationships whichmay be attained through the control system of Figure 1.

For a complete showing and fuller description of a flash welder platenmovement control means to which the present invention is applicablereference is made to U. S. Patent 2,313,226, assigned to the assignee ofthe present invention.

Referring to the drawing, reference numeral l designates the normallyfixed platen of a flash-butt welder while reference numeral H is themovable platen which ma be hydraulically operated by the apparatus andin the manner disclosed in the above mentioned patent. In accordancewith said disclosure there is an operating lever |2 which, withincertain limits, may effect movement of the platen under complete manualcontrol but when the lever is moved to the left to latched position themovement of the platen H is under automatic control of the cam and thefollow valve. Welding current is furnished by a transformer |3 having atapped primary winding l4 having one of its end terminals connected withthe current source through conductor I5. To enable maximum use to bemade of the principles of the invention we employ a pair of regulatorsconnected in parallel with the respective taps of the primary winding14, these regulators having movable contact arms l6 and I1,respectively. To complete the energizing circuit for the transformer l3through the regulator arm It We provide a circuit consisting of theconductor l8 and electronic contactor I9 and conductors and 2|, thelatter of which is connected with the source. A suitable circuitcontrolling device, preferably the electronic contactor 22 is employedin a circuit consisting of a conductor 23 and conductors 20 and 2| toenergize the transformer l3 through the regulator having arm IT.

The electronic contactor 22 consists of a pair of ignitrons 24 and 25connected back-to-back and each having an anode firing ignition circuitmade possible by the associated rectifiers shown, which rectifiers arepreferably of the dry disk type as will be understood. These ignitioncircuits have a common lead and, in the embodiment of the inventionillustrated, a pair of controlling switches is placed in this lead--thecircuit being traceable from the junction of the rectifiers associatedwith the ignitron 24 through conductor 25, contactor 21 of a relay 28,conductor 29, conductor 30, the common contact of a double throw limitswitch 3|, contact 32 of switch 3|, and conductor 33 to the junction ofthe rectifiers associated with the ignitron 25. It will be obvious thatupon closure of both these switches in this return circuit the contactor22 will conduct the major part of the successive positive and negativehalf cycles of the source current.

The electronic contactor |9 comprised of the back-to-back connectedignitrons 34 and 35 has similar anode firing ignition circuits alsohaving a common return conductor in which are similar controllngswitches but with the very important diflerence that in this returnconductor there is additionally included a full-wavecontrolled-conduction device consisting of a pair of gaseous dischargedevices 36 and 31 connected in inverse parallel. Thus, the circuit ofthe common return in the ignition circuits of contactor l9 may be tracedfrom the junction of the rectifiers associated with ignitron 34 throughconductor 38, cathode of tube 36 (anode of 31), anode of tube 36(cathode of tube 31) conductor 39, contactor 40 of relay 4|, conductor42, contact 43 of switch 3|, and conductors 30 and 44 to the junction ofthe rectifiers associated with the ignitron 35. It will be obvious thatupon closing of the switches 3| and 40 in the above described commonreturn circuit the ignitrons 34 and 35 are fired during the respectivepositive and negative half cycles of the source current at timesdetermined by the phase relation of the periods of conduction in thegaseous discharge devices 36 and 31.

In order to correlate the electrical control sys tem disclosed hereinand particularly the voltage shifting features thereof with themechanical operation of the welding machine we provide a number ofmanual switches and a number of automatically operated limit switches,the latter of which are arranged to be operated in accordance with theprogression of the movable platen during the welding cycle. Thus, theselimit switches may be operated either directly by the platen or by theposition of a slide as shown in the above mentioned patent which slidemounts the cam determining the pattern of movement of the platen. In thedrawing, such limit switches are shown at 3|, 45, and 45 and by way ofexample switch 3| may be so adjusted that it is actuated shortly afterthe work pieces held by the platens begin flashing during forwardmovement of the movable platen Switch 45 may be adjusted to close at anytime during the flashing period and switch 46 is adjusted to close atpoint of upset. A thumb switch 41 is mounted on the operating arm l2 andthe switch 48 is mounted on the control linkage structure in such amanner that it is closed when the arm i2 is latched in the positionshown for complete automatic operation of the machine. We provide acontrol relay 49 which is arranged to be energized from a transformer 55(deriving energy from the source through conductors 2| and 5|) throughthe circuit comprised of conductors 52 and 53, switch 41, conductor 54,coil of relay 49 and conductors 55 and 56. Upon energization of relay49, relay 4| is energized through the circuit-line conductor 56,conductor 55, contactor 51 of relay 49, conductor 58, normally closedcontact 59 of a time delay relay 6!], conductor 5|, coils of relay 2Band 4| (in parallel) and conductors 62 to line conductor 52. As shown,contact 32 of switch 3| is normally closed so that immediately uponenergization of relay 2B the contactor 22 is now conditioned for fullconduction and the welding transformer I3 is energized to an extentdeter mined by the setting of the regulator arm l1. This pre-set voltagevalue may be employed for the pre-heating of the work pieces in certainclasses of work, the pieces being jammed together by manipulation of thearm i2 in the manner explained in the above mentioned patent, or in thecase of strip welding, for example, this initial voltage may be set atthe maximum available on the machine and utilized to align or conditionthe strip edges preparatory to the welding proper as explained above. Weprovide another control relay 63 adapted to be energized upon closure ofswitch 48 through the circuit-conductors 525 and 64, coil of relay 63,conductor 65, switch 48, and conductors 66, 53, and 52. Energization ofrelay 53 closes a holding circuit comprised of a contactor 61 on relay63 for continuing the energization of relay 49 upon the release of thumbswitch 41 so that the operator may take his hands enregulator arm I I isset.

eases and under the settings herein specified the initial flashingvoltage will be the voltage at which the This is illustrated by line Ain Figure 2. As the flashing proceeds, switch 3| is actuated and contact32 opens While 43 is closed thus opening the common return in theignition circuits for contactor 22 while closing the common return inthe ignition circuits for contactor l9 and contactor 22 willthereuponcease to conduct.

Conditioning of the ignition circuits for the ignitrons of contactor l9will cause this contactor to conduct such portions of the successivehalf- Waves of the current source as is predetermined by the phaserelation of the periods of conduction in the tubes 35 and 31. A fixedsetting of the voltage applied to the welding load during this time is,of course, furnished by the position of the regulator arm it. The phaserelation of the periods of conduction in the tubes as and 3 iscontrolled by 'a phase shifting circuit, indicated generally by thereference numeral 18, the output of which is connected across theprimary winding of an impulse transformer 'il. Circuit 10 includes theserially connected potentiometers 1'2, 13 and 14, capacitance l5, andinductances comprising the two sections of a center tapped primary of abiasing transformer 16. We provide a control relay 1'! having a normallyclosed contactor 18 which shorts out the potentiometer 13 and normallyopened contactor is which is connected to short out the potentiometer 12upon energization of the coil of the relay. Thus, when relay 7'! isde-energizedthe resistance leg of the phase shifting circuit is made upof resistances -72 and 79 but upon energization of relay 71 theresistance leg is made up of resistances 13 and 14. By varying therelativesettings of the potentiometers "l2 and 13 the phase deviationangle may be pre-set for both the opening and the closing of the relay11.

The primary winding of transformer 16 is connected across a suitablealternating voltage source comprised of the secondaryof a transformer 88which in turn has its primary connected with the common source ofalternating potential, Transformers ll and 16 each have two secondarywindings for the grid control circuits of the tubes 36 and 31. Thecontrol circuit for tube control circuit for tube 31 the cathode thereofthrough the secondary winding 75B of transformer -76 andsecondarywinding MB of transformer H to the control grid thereof.

The coil of relay 1! is in a circuit which may be traced from the lineconductor 56 through conductor 8i, contactor 82 of relay 83, conductor83, coil of relay 17, conductor 84, switch 45, and conductors 85 and 53to line conductor 52. Relay 63 is normally energized during the weldingcycle to hold contactor 82 closed so that at any desired time during theflashing period as deter in the tubes 35 and 31. Normally it isdesirable to reduce the voltage applied to the work pieces afterflashing has progressed for appreciable time and therefore potentiometer13 will be normally set to effect, when it is brought into the shiftingcircuit, a. further delay in the firing of the tubes 36 and 31 withrespect to t e anode-cathode potential appearing at the ignitrons 34 and35.

Reference numeral 86 designates a control solenoid which is operative,when energized, to eifect quick up-setting movement of the platen I Ithrough suitable means, not shown, and is arranged to be energized uponthe closing of contactor 81 of relay 88. The energizing circuit for thecoil of the latter may betraced from conductor 56 through conductor 8|,contactor 82, conductor 89, coil of relay 88, conductor 9!), switch 46,and conductor 85 and 53 to conductor 52. In the specific circuitillustrated, the voltage at upset is the same as the final flashingvoltage, as shown by line A in Figure 2, but it will be obvious to thoseskilled in the art that by the use of suitable conventional controlrelay devices the system may be adjusted either to cut off the currententirely at point of upset or to raise or at point or upset as desired.Thus, additional potentiometers may, if desired, be inserted in theresistance leg of the phase shifting circuit together with accompanyingrelays having shorting contactors arranged to be actuated at anypredetermined time during the welding cycle.

In the circuit illustrated, the coil of the time delay relay 60 isenergized and conductors 85, Upon relay 60 timing out its period, boththe relays 28 and 4| are de-energized and all the ignition circuits foropened at this time. To retract the slide back to its initial startingposition the lever I2 is moved to the right, as viewed in Figure 1,thereby opening switch 48 and restoring the other switches 31, 45'and45. Opening of switch 48 tie-energizes relay 63 which in turnde-energizes relay 4'! and itial condition preparatory ing cycle ofoperation.

The above specifically described circuit embodiment of the inventionshould be considered merely as illustrative since the invention isconsidered to reside as much in the correlation of the disclosed controlmethods and system with the mechanical operation of the welder as withthe control methods and system per se. A wide variety of coordinationsmay be effected and. some of these are illustrated in Figure 2, Thusline B represents a cycle wherein the voltage is dropped at the start offlashing, further reduced during flashing, and sharply increased at theflashing and by utilizing a take-over relay to restore conduction incontactor 22 at the point of upset. Curve 0 illustrates a cycle wherein'cycle F a high 'complishes the ob ects initially set out.

plished simply by backing of! and rendering inoperative the switch 45and adjusting switch 3| to change over at the beginning of flashing. Inthe cycle E the preheating and flashing voltage is constant while ahigher upset voltage is used and to accomplish this, switch 31 may beadjusted to hold contactor 43 closed at all times while switch 45 isadjusted to close at point of upset and circuit 10 is adjusted to bringthe conduction periods in tubes phase with the alternations of thesource. In flashing voltage is used while the upset voltage is less andthis may be scheduled by the setting of potentiometers l2 and 13 as willbe understood.

It should now be apparent that we have provided an improved voltagecontrol system for an electric resistance flash-butt welder which Tare}-e control provides for the application of a substantially infinite rangeof voltages to the work pieces and enables the voltage to be abruptlyshifted from one value to the other during the welding cycle. Moreover,the system may have such operating characteristics, if properlyadjusted, that high voltage may be applied to square or condition theedges of the work pieces preparatory to the actual welding cycle afterwhich lower and program-stepped voltages may be applied in effecting theactual welding operation. In general, the control system of theinvention is capable of being so correlated with the welding machinethat optimum heatin and flashing conditions may be obtained in allclasses of work and under all conditions of operation.

Since, as explained above, the specific circuit arrangements disclosedherewith are capable of wide and obvious modifications, depending on theparticular character of the work at hand, reference should be had to theappended claims in determining the scope of the invention.

What we claim is:

1. A voltage control system for a flash-butt welder having a movableplaten comprising in combination a welding transformer having a tappedprimary winding and a secondary adapted to be connected to the workpieces, a current source, a controllable conducting meansinterconnecting said source with one of the taps of said primarywinding, a pair of ignitrons connected in inverse parallel intermediatesaid source and another of the taps of said primary winding and eachhavin an ignition circuit, means to condition said conducting means atthe start of the welding cycle, means to control said ignition circuits,and means operable automatically upon predetermined advanced movement ofsaid platen to render inoperative said conducting means while actuatingsaid means to control in such manner that said ignitrons are renderedconducting, said means to control further including means to render saidignitrons conductive at predetermined adjustable times during thesuccessive half-waves of the voltage alternations of said source.

2. A voltage control system for a flash-butt welder having a movableplaten comprising in combination a welding transformer having a tappedprimary winding and a secondary adapted to be connected to the workpieces, a current source, a controllable conducting means connectingsaid source with one of the taps of said primary winding, a pair ofignitrons connected in inverse parallel intermediate said source andanother of the taps of said primary winding, an

36 and 3'! closer in ignition circuit for said ignitrons, a pair ofcontrol circuits for said ignition circuits operative to condition saidignitrons at diilerent times during the successive alternations of saidsource whereby the value of the effective current transmitted by saidignitrons may be varied, means to condition one of said pair of controlcircuits, and means operative in response to said platen attaining apredetermined advanced position to condition the other of said pair oi":control circuits while rendering inoperative the said one of said pairof control circuits.

3. A voltage control system for a flash-butt welder having a movableplaten and a lever for manually controlling the movement of said platenat least during the initial part of the welding cycle, a weldingtransformer having a tapped primary winding and a secondary adapted tobe connected to the work pieces, a current source, a controllableconducting means connecting said source with one of the taps of saidprimary winding, a pair of ignitrons connected in inverse parallelintermediate said source and winding, an ignition circuit for saidignitrons, a pair of control circuits for said ignition circuitoperative to condition said ignitrons at different times during thesuccessive alternations of said source whereby the value of theeffective current transmitted by said ignitrons may be varied, manualmeans associated with said lever to activate said controllableconducting means, means responsive to said lever attaining apredetermined advanced position to condition one of said pair of controlcircuits, and means operative in response to said platen attaining apredetermined advanced position to condition the other of controlcircuits while rendering inoperative the said one of said pair ofcontrol circuits.

4. A voltage control system for a flash-butt welder having a movableplaten and a lever for manually controlling the movement of said platenat least during the initial part of the welding cycle, a current source,manual means associated with said lever to initiate flow of current fromsaid source to the work pieces, means to control the flashing currentcomprising a pair of ignitrons connected in inverse parallel betweensaid source and work pieces and having an ignitron circuit, phaseshifting means controlling said ignition circuit whereby the value ofthe effective current transmitted by said ignitrons may be varied,control means coupled with said phase shifting means and operative uponsaid lever attaining a predetermined advanced position to transmit onecurrent value to the work pieces, and control means coupled with saidphase shifting means and operative upon said platen reaching apredetermined advanced position to transmit another value of current tosaid work pieces.

5. The method of flash-butt welding which consists of applying analternating current to the work pieces being welded to initiate flashingtherebetween, and reducing the effective value of said current duringthe flashing period by re- 55 ducing the portions of the consecutivehalf cycles of the current source transmitted to said work pieces.

6. The method of flash-butt welding which consists of applying analternating current to the work pieces being Welded to initiate flashingtherebetween, and reducing the effective value of said current byreducing at a predetermined time during the welding cycle the portionsof the consecutive half cycles of the current source transmitted to saidwork pieces.

10 REFERENCES CITED The following references are of record in the fileof this patent:

cycles of the current source transmitted to said 10 sections.

JOSEPH H. COOPER. CLYDE E. SMITH.

5 UNITED STATES PATENTS Number Name Date 1,916,012 Otto June 27, 19331,916,013 Otto June 27, 1933 FOREIGN PATENTS Number Country Date 559,658Great Britain Feb. 24, 1944

